1. Field of the Invention
The invention relates to an expansion device, and, in particular, relates to an expansion device applicable to a mobile device.
2. Description of Related Art
In recent years, mobile devices such as cell phones, handheld game consoles, tablet devices or notebooks have become popular electronic devices due to research, development, and promotion by technology industries in the United States, Europe, Japan and Korea. With the progress of technologies, mobile devices have also become parts in people's life. However, it is well-known that no matter how great the touch-control functions of a mobile device such as a tablet device are, or how sensitive the virtual buttons (keyboard) are, some people are still more accustomed to inputting texts or giving instructions for operating a tablet device via physical keyboards. In particular, when a button of the physical keyboard is pressed, the springiness of the button relieves the pressure of fingers, which is more comfortable than using fingers to touch the hard glass-surface of the tablet devices.
Accordingly, a lot of removable keyboards have appeared in the market. The removable keyboards may optionally be assembled with tablet devices, such that users can easily type on the physical keyboards when they need to input texts or give instructions of operating. On the other hand, when the users don't need keyboards, the removable keyboards can be removed from the tablet devices to make the tablet devices become light, thin and easy to be carried again.
However, current removable keyboards simply provide an advantage that they can be easily assembled with the mobile device, while providing less additional capabilities or functionalities. Compared with functionalities such as document processing and enjoyment of visual effects provided by tablet devices, removable keyboards cannot effectively assist in providing miscellaneous functions of mobile devices, such that the demands of people for e.g. enjoyment of visual effects cannot be satisfied. In addition, removable keyboards cannot provide functionalities of screen protection to mobile devices as well.